CO2 Enrichment

Keesje said:

I had a discussion about this in another thread.
'Stale air' and 'fresh air' are ways us humans experience air quality.
We feel uncomfortable in a room with a high humidity and high levels of CO2.
Then we open a window to let fresh air in and level out the CO2 level.
So for example from 1200 ppm back to 450 ppm.

Plants don't have that problem.
There is always plenty of O2 in a room (air contains about 20% of O2 and before the roots could absorb all the O2 in your room - even if it would be 100% sealed (which it never is) - it would take weeks and weeks.
CO2 levels can hardly get too high, and I also think you control that very well.
So not need to vent for those reasons.

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What co2 level would be too high after plants exhale the co2 during night cycle that would require to vent out at nights you think?

I got my co2 monitor set at 1200ppm for daytime but once the lights go off and the plants exhale co2 throughout the whole night cycle..... towards the end when I go inside right before lights turn back on my co2 monitor reads ~2400ppm sometimes less.... but above 2000ppm everyday towards the ending weeks of harvest. Its a sealed room; no venting in or out.

The extra co2 is nice for the next day cycle but Idk maybe this co2 ppm is too high and I should vent out at nights? Id like your opinion on the matter.

XtraGood said:

@DoubleAtotheRON You mentioned that after growing there for a few years you would change some things if you did it again from scratch. I was thinking about building a smallish metal shop type building in the not too distant future and am getting a features list together, not much on the list yet: concrete pad, floor drains, insulation (what type?), sealed, mini-split, 220v, __________. Any advice you have I'd happily take.

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Man, I'd say you can't have too many outlets... I'd put them on the ceiling, .. everywhere. In hindsight, I wished I would have built it out with more rooms for drying/curing.. we do have a room for that, but it's crowded at harvest. We still have about 300 sq ft under the roof that is now my really downsized man shop, but we were just talking about this tonight about building another shop for all my shit.. tractor, mowers, tools, air compressor, etc, and taking that 300 Sq ft, and building it out for just drying, curing, and mother/clone room. We did have the foresight to frame the processing room for a door in case we did do this, so that would work out. Bottom line, if you want to produce ~25 lbs of product, you're going to need 1500 sq ft for the grow, processing it (trimming), drying, curing, weighing, packaging, labeling, etc.... we're going to look into quotes to finish out that 300 and for another shop for my shit.... I hate leaving expensive equipment outside. Otherwise, insulate the shit out of it. We did 2 outside walls at 8 inches, spray foam insulation, and the other 2, 6 inch spray foamed, and the ceiling at 12 inches spray foamed. Its super efficient.. I was just telling another member today that I am struggling to get the room to 86 degrees with the new Co2 system, 2 rows of 3 lights running, dehuyes pumping hot air.. and I have the AC set at 80... I can't seem to get any hotter than 84 short of shutting the AC off completely. .. working on that extra 2 degrees I need, and it's hot as fuck here right now weather wise.

newbplantgrower420 said:

What co2 level would be too high after plants exhale the co2 during night cycle that would require to vent out at nights you think?

I got my co2 monitor set at 1200ppm for daytime but once the lights go off and the plants exhale co2 throughout the whole night cycle..... towards the end when I go inside right before lights turn back on my co2 monitor reads ~2400ppm sometimes less.... but above 2000ppm everyday towards the ending weeks of harvest. Its a sealed room; no venting in or out.

The extra co2 is nice for the next day cycle but Idk maybe this co2 ppm is too high and I should vent out at nights? Id like your opinion on the matter.

Click to expand...

I had the same question.... I wouldn't worry about it. You just have the extra CO2 in there when the lights come on, and your system can save some fuel by waiting for the level to drop as they start eating it up and its not cycling for a while after lights on.

newbplantgrower420 said:

What co2 level would be too high after plants exhale the co2 during night cycle that would require to vent out at nights you think?

I got my co2 monitor set at 1200ppm for daytime but once the lights go off and the plants exhale co2 throughout the whole night cycle..... towards the end when I go inside right before lights turn back on my co2 monitor reads ~2400ppm sometimes less.... but above 2000ppm everyday towards the ending weeks of harvest. Its a sealed room; no venting in or out.

The extra co2 is nice for the next day cycle but Idk maybe this co2 ppm is too high and I should vent out at nights? Id like your opinion on the matter.

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Don't you do any venting?
How do you prevent smells to escape by creating under pressure?

Normally 1500 is about the max for most plants, but because plants don't absorb CO2 in darkness.... mmm, tough question.

Keesje said:

Don't you do any venting?
How do you prevent smells to escape by creating under pressure?

Normally 1500 is about the max for most plants, but because plants don't absorb CO2 in darkness.... mmm, tough question.

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No venting at all. Completely sealed room.

I have a recirculating carbon filter to hide the smell. It does a decent job. Youd have to be right in the front of the door entrance to smell anything.

Ive done it this way for years and its been fine all this time but I was wondering if the grass is greener on the other side. If venting out the excess co2 out at nights would give me better results.

Lets say I vent out air including the co2 would it make it there would be more oxygen available for night cycle for the plants? I dont really want to bring air in though. Id like to only push out.

DoubleAtotheRON said:

I had the same question.... I wouldn't worry about it. You just have the extra CO2 in there when the lights come on, and your system can save some fuel by waiting for the level to drop as they start eating it up and its not cycling for a while after lights on.

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ya makes sense. btw how does that spartan series monitor work?

My setup consists of just a basic co2 ppm monitor and my split ACs I have on auto at the degrees set and dehumidifier has a set humidity on the unit when it starts dehumidification at. Would the Spartan series be worth it for my setup?

My temps fluctuate like 15 degrees between day and night cycle

newbplantgrower420 said:

Lets say I vent out air including the co2 would it make it there would be more oxygen available for night cycle for the plants? I dont really want to bring air in though. Id like to only push out.

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There is plenty of O2 in you room.
More then your roots can absorb in weeks.
So for that, you don't need to do it.

To my knowledge plants are not able to absorb CO2 during nighttime.
But I am not sure if really high levels could even be hurting the plant. I don't think it will hurt them, but I just don't know, so I will give you no advice on this.

If your results are fine, don't change a thing.
Otherwise you might try to do some venting in the dark hours.

Edit: I was also not aware that plants produce that much CO2 themselves at night. I know that CO2 in nature are higher during nighttime, but 2000 in a sealed room does surprise me.

newbplantgrower420 said:

ya makes sense. btw how does that spartan series monitor work?

My setup consists of just a basic co2 ppm monitor and my split ACs I have on auto at the degrees set and dehumidifier has a set humidity on the unit when it starts dehumidification at. Would the Spartan series be worth it for my setup?

My temps fluctuate like 15 degrees between day and night cycle

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The Spartan is a Total Environmental Control.. you can hook up your CO2 burner, dehuyes, evap cooler, AC, Heat, and it controls it all. All I have hooked up is the sniffer, the CO2 burner, and an Evap cooler. I set the CO2 at 1200 with a 100ppm deadband. So it will hit 1199, and burn till the room reaches 1300 (100 deadband), and then it will kick off till it floats back down the 1199. The Evap cooler is plugged into the humidity input. I set it at 50, so when the RH gets to 49, it will kick in the Evap Cooler to 55, and shut it off. Meanwhile, my Dehuyes have their own set limits, and I set them to dehumidify at 60.. So, all this shit is kicking in and out all day balancing everything out. All I have to do is make sure there is water in the evap cooler.

DoubleAtotheRON said:

So, all this shit is kicking in and out all day balancing everything out.

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It's cool to look at a temp / humidity / co2 chart and see the little wiggles of the deadbands, day / night set point changes... A good environmental controller is mandatory. I have one in each room and they are like little room gods lol.

Renfro said:

It's cool to look at a temp / humidity / co2 chart and see the little wiggles of the deadbands, day / night set point changes... A good environmental controller is mandatory. I have one in each room and they are like little room gods lol.

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Yes they are!.. and Im lovin' it!

newbplantgrower420 said:

I got my co2 monitor set at 1200ppm for daytime but once the lights go off and the plants exhale co2 throughout the whole night cycle..... towards the end when I go inside right before lights turn back on my co2 monitor reads ~2400ppm sometimes less.... but above 2000ppm everyday towards the ending weeks of harvest. Its a sealed room; no venting in or out.

Click to expand...

For my understanding...
During the dark period you don't add any CO2 at all?

From my readings, venting during the night cycle may be helpful.

Snippet...



...from this article.


Night venting has improved my grows, but its only 4x8x8. Possibly more susceptible to low o2 than large grows.
Also helps keep my rh curve flat.

I doubt those statements very much.
There is so much O2 in a cubic meter of air.
Way, way more then the roots can absorb.

Tomatoes for example consume about 200 mg of O2 per hour per kilo of roots.
But let's for the sake of discussion say that roots of cannabis consume 500 mg of O2 per hour per kilo of roots.
And let's say that on a square meter you have 10 kilo of roots (it is less, but for discussions sake)
So the roots would consume 500 mg x 10 (kilo) per hour. = 5000 mg
In 1 day that is 24 x 5000 mg = 120.000 mg.

A cubic meter of air contains 21% O2.
O2 weights 1,430.000 mg per cubic meter.
So 1,430,000 mg x 0,21 = 300.000 mg of O2.

So even in this theoretical example there would be enough O2 for 2,5 days.
But in reality way more, because the roots absorb less O2 then 500 mg, 10 kilo of roots on 1 square meter is a lot, and your grom room would not be 1 cubic meter, but more likely 2,5.

Keesje said:

For my understanding...
During the dark period you don't add any CO2 at all?

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No. The photocell on the sniffer disables it during lights off. My CO2 levels do not drop much after lights out. Mainly staying over 1000-1100.
Edit: Shit, sorry I thought you were talking to me.

Keesje said:

For my understanding...
During the dark period you don't add any CO2 at all?

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none at all. The monitor has a photocell.

I do have 90 plants though. Each one exhaling some co2 at night will bump the co2 levels up pretty quickly.

Thank you for the interesting numbers.
There are not many growers who have a 100% sealed room.
So it's great to hear about these numbers.

Would be a nice experiment if you could succeed in having another (smaller) room next to your big room.
Then, during the dark period of the big room when the plants produce CO2, to let that CO2 flow to the small room with a light-period.
And thus give the plants in there extra CO2.
I think, that it will be not enough, but it would be a nice experiment.

XtraGood said:

insulation (what type?)

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spray foam

How sealed does a room need to be to keep the CO2 around? Is a room in a house sealed enough if you only exhaust at lights out and seal all the windows doors and vents?

That is sealed enough.
Most growers who run CO2 have a small exhaust fan with filter, to create under pressure, so smell can not escape.
So even that is ok.

I am looking at getting a Autopilot APC8200 Monitor & Controller; I am still looking for a regulator that seems better than the others. I would just order the vivosun off amazon but I am not sure what breaks quick and what is solid yet. Thinking about CO2 Tank system in 15x10 or 15x20 room